Note: You cannot add to RFID locks directly. You must write data into by a 125kHz RFID card writer use. They are blank tags, no data inside. Sensing Distance: 2.5 to 10 cm (1 to 4 inch); Data Storage Life: 10 Years.Writable Rewritable Frequency: 125 KHz Chip type: T5577 Type: Read and rewrite key tags Waterproof: Water resistant Colour: blue Material: ABS Size: about 27.5 x 35 x 4mm Package Contents: 50 x Writable 125kHz RFID Key Fob Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.